[60 Melodies to Choose From]: The doorbell offers 60 different chimes for you to select. It also has 4 adjustable volume levels - Loud, Medium, Soft, and Mute [120dB Loud Volume]: The receiver's maximum volume reaches 120 decibels, ensuring the doorbell can be heard throughout your home, so you never miss a visitor [Battery-Free Transmitter]: The wireless doorbell transmitter doesn’t require batteries. It operates by generating power through pressing, making it eco-friendly and maintenance-free [250m Wireless Signal Range]: This doorbell has a long-range signal, capable of transmitting up to 250 meters in an open space. The strong RF signal can penetrate steel doors, wooden doors, and walls (note: distance is measured in an open area) [Different Chimes for Front and Back Doors]: When paired with two or more transmitters, you can set different chimes for each. Simply choose the melody on the receiver before pairing, and the transmitter will lock in the selected tune. This feature helps distinguish between visitors at different doors [IP44 Waterproof Rating]: With an IP44 waterproof rating, the transmitter is weather-resistant for daily use (outdoor use with a waterproof cover is recommended, not include the waterproof cover) [Low Power Consumption]: The receiver uses only 0.25W, consuming about 1 kWh per year [Ideal for Various Settings]: Utilizing RF433 high-frequency technology, this doorbell is highly resistant to interference, allowing multiple units to operate without cross-talk. It's perfect for homes, schools, offices, hospitals, restaurants, and factories [Easy Installation and Use]: Simply plug the receiver into a power outlet. The transmitter can be mounted using double-sided tape or screws Specifications: Power: Self-generating (no battery required) Power Consumption: 0.25W Music: 60 options Volume: Up to 120dB Transmission Range: Over 250m (open area) RF Frequency: 433MHz Operating Temperature: -20℃ to 60℃ Notes: Do not install the transmitter on iron doors as metal can interfere with the RF signal. Install it beside the door instead. The signal range is measured in an open space. The more obstacles present, the more the range is reduced.